This invention relates to a novel process for the electrophilic ring fluorination of aromatic compounds and to novel fluorinated aromatic compounds.
The fluoroxyfluoromethanes utilized as fluorinating agents in the process of this invention include fluoroxytrifluoromethane (CF.sub.3 OF) and bis-(fluoroxy)-difluoromethane (CF.sub.2 (OF).sub.2). The synthesis of fluoroxytrifluoromethane was first disclosed by Kellog and Cady, J. Am. Che. Soc. 70 9386 (1948). See also U.S. Pat. No. 2,689,254 to Cady and Kellogg . The reaction of fluoroxytrifluoromethane with benzene in the vapor phase, catalyzed with a spark or ultraviolet light, has been shown to occur explosively with the production of low yields of fluorobenzene; Allison and Cady, J. Am. Chem. Soc. 81 1089 (1959).
D. H. R. Barton et al. disclosed the reaction of fluoroxytrifluoromethane with saturated hydrocarbons, alkenes, and certain aromatic derivatives, amines and amides; J. Am. Chem. Soc. 98 3034 (1976); J. Chem. Soc. Perkins I 1974, 739; Chemical Communications 1968, 804; J. Chem. Soc. Perkins I, 1980, 712; 1974, 739.
Kollonitsch, U.S. Pat. No. 4,030,994; J. Am. Chem. Soc. 92, 7494 (1970) has disclosed the reaction of certain aromatic substrates under conditions conducive to the formation of free radicals.
The preparation of bis-(fluoroxy)-difluoromethane was first reported by P. G. Thompson; J. Am. Chem. Soc. 89 1811 (1967); and by Prager and Thompson; U.S. Pat. No. 3,420,866. U.S. Pat. No. 3,585,218 to Talbott discloses the reaction of bis-(fluoroxy)difluoromethane with certain aromatic substrates, such as benzene, nitrobenzene, naphthalene, and with pyridine to produce ring fluorinated products.
The ring fluorination of certain aromatic compounds, such as acetanilide, anisole, nitroanisole, dimethoxybenzene, methoxynaphthalene and methyl hydroxybenzoate by reaction with acetyl hypofluorite is disclosed by Lerman, Tor and Rozen; J. Org. Chem. 1981, 46, 4631. The investigation of such reactions involving acetyl hypofluorite with various aromatic substrates is expanded and disclosed in greater detail by Lerman, Tor, Hebel and Rozen in J. Org. Chem. 1984, 49, 806.
The prior art does not indicate that N-substituted anilines will react with fluoroxyfluoromethanes to yield electrophilic aromatic substitution products. In U.S. Pat. No. 3,917,688 to Barton et al, there is disclosed the preparation of N-fluorinated amides and amines on treatment of an acid amide with a hypofluorite including fluoroxytrifluoromethane, indicating that reaction occurs at the nitrogen atom, not on the aromatic ring. Patrick et al., J. Org. Chem. 41 3413 (1976) discloses examples of fluoroxytrifluoromethane undergoing addition reactions with polynuclear aromatic substrates. Barton et al., Chemical Communications 1968, 806, and in U.S. Pat. No. 3,687,943 teaches that the reaction of fluoroxytrifluoromethane with steroids results in the addition of fluorine to the aromatic steroid substrate, in preference to substitution of fluorine on the aromatic ring. In reactions of fluoroxytrifluoromethane with aromatic substrates wherein substitution reactions are indicated, it is taught that conditions conducive to a free radical process are necessary; see U.S. Pat. Nos. 4,030,994 and 3,775,444.